A hybrid vehicle includes an internal-combustion engine and a motor for running. The hybrid vehicle drives the motor with electric power supplied by a power source apparatus mounted thereon and uses the motor as a driving source for the vehicle.
The hybrid vehicle can run by using one or both of the internal-combustion engine and the motor for running as the driving source. For example, the hybrid vehicle can stop the engine and use only the motor as the driving source for running, or can use both the internal-combustion engine and the motor as the driving source for running. The power source apparatus can be charged with electric power from regenerative braking in decelerating the vehicle or electric power generated by the internal-combustion engine.
For example, a lithium-ion secondary battery for use as the power source apparatus may experience precipitation of lithium metal on the surface of a negative electrode due to use conditions. Since the precipitation of lithium metal may reduce the battery performance, control is performed to adjust (limit) an electric power which can be input to the power source apparatus in order to suppress the precipitation of lithium metal.
When an accelerator pedal is released to brake the vehicle, however, the limitation of the electric power which can be input to the power source apparatus reduces the regenerative braking force (regenerative brake) of the motor, and accordingly, it is necessary to apply a larger braking force of an engine brake from rotational resistance of the engine. Since the application of the larger braking force of the engine brake increases the RPM of the engine, the engine emits more exhaust gas and air to be supplied to a catalyst for exhaust gas purification. The increased amounts of exhaust gas and air to be supplied to the catalyst for exhaust gas purification may promote the deterioration of the catalyst for exhaust gas purification.